After installing XP Service pack 3 you might find your internet connectivity and/or network connectivity becomes a bit dodgy. So you might consider going to windows update to see if there’s a new driver only to find a problem occurs and windows is unable to continue on the windows update site.
The problem: it appears that certain OEM editions (those which come with PCs at time of shipping) of XP have certain configurations which cause Service Pack 3 to fail the installation of windows update v.3, and as a result the required files are not properly installed.
The solution: manually download windows update v.3 and force the application to re-install.
download to your c: drive then start up command prompt (programs/accessories/command prompt) then type WindowsUpdateAgent30-x86.exe /wuforce
once its run, reboot your pc, go to windows update and then install all the updates you’ve missed!
For more info see the information from microsoft : http://support.microsoft.com/kb/943144